1. Field Of The Invention
This invention relates to a hydraulic actuator and, particularly, to a hydraulic actuator for effecting bidirectional axial displacement of a shaft.
2. Description Of The Prior Art
There are certain applications wherein rotating or nonrotating shafts must be moved axially for various reasons, such as actuating switches or other actuator purposes during a particular mode of operation. For instance, rotors on a generator may be shifted angularly to control loading parameters by axial movement of a driving shaft. The axial movement of the shaft most often is effected by using a conventional hydraulic piston on one end of the shaft. Heretofore, the hydraulic fluid flow and pressure operating on the piston has been provided by a rather complex hydraulic system employing pumps, numerous valves, complex accumulators, piping/coring and like components. Such a system or structural arrangement not only is too heavy, complex and expensive for many applications, but such systems are rather inefficient.
Rotating and reciprocating systems also are used on various tool applications, such as thread tapping tools or the like. For instance, U.S. Pat. No. 3,388,548 to Bieths, dated June 18, 1968, shows a rotating and reciprocating shaft splined to a motor for rotation thereby. The rotating shaft is reciprocally movable in an axial direction relative to the motor and extends into a cylinder. The cylinder is stationary and the shaft has a piston in the form of pump means defined by a vane-type pump arrangement. Fluid communication is established through the cylinder on opposite sides of the vane pump for effecting axial movement of the shaft in response to rotation of the shaft. Such a construction also is rather complicated and involves quite a number of movable parts for constructing and assembling the vane pump-piston within the stationary cylinder.
The invention is directed to providing a new and improved hydraulic actuator of the character described above and which overcomes one or more of the above problems.